1. Field:
This invention pertains generally to intravenous catheter systems used in monitoring arterial functions and in the infusion of medical fluids to a patient. In particular, the invention relates to flow apparatus for controlling the flow of fluid at a desired continuous rate and to provide for intermittent, manually controlled larger flows of fluid to rapidly flush the catheter system.
2. State of the Art
Intravenous catheterization is a very useful procedure available for clinical monitoring of blood system and related parameters including arterial pulse waveform, stroke volume, heart rate, cardiac output, duration of systole, and systolic, diastolic and mean pressures. In addition, blood can be withdrawn for blood gas analysis.
To provide reliable operation over periods which may amount to several days, it has been found essential to flush the catheter continuously during its use with a regulated, continuous infusion of a relatively small flow of a liquid to prevent occlusion of the intravascular end of the catheter by blood coagulation. Continuous flushing systems have been proposed which utilize capillary tubes as flow resistors, with the flushing solution flowing therethrough under pressure. See, for example, U.S. Pat. No. 3,675,891, issued to Gordon S. Reynolds, et al. on Sept. 18, 1970, and an article appearing on pages 675-678 of the Journal of Thoracic and Cardiovascular Surgery, Volume 57, No. 5, May 1969.
Generally, the prior systems employed an objectionable large amount of apparatus including numerous stopcocks, with resulting loss of fidelity in the operation of the system. The device disclosed in U.S. Pat. No. 3,675,891 overcomes many of the deficiencies inherent in he earlier systems by providing a relatively small unitary piece of apparatus which was constructed so as to eliminate the use of all stopcocks. A resilient valve was provided to control a bypass around the capillary flow resistor, with the valve being operated by manually pulling a valve stem which extends longitudinally from the apparatus. The valve and step system of such device, however, has certain drawbacks. For example, the protruding stem is subject to entanglement in tubing, bedding, or other paraphenalia resulting in possible undesired opening of the valve or breakage of the valve stem so as to preclude proper operation of the device. The valve stem can also be broken by pulling the stem to one side or the other rather than longitudinal, and the valve has also been found to occasionally fail in the open position. In addition, the valve and stem system is generally difficult to operate with one hand, and for all practical purposes, requires two-handed manipulation.
3. Objectives
The principal objective of the present invention is to provide an improved regulating device which is reliable and easy to operate, as well as being simple in construction. A particular objective of the invention is to provide a small, streamlined device for connection in the catheter system which can be operated easily with one hand and which does not include stopcocks or stem actuated valves as in the devices of the prior art.